Protective treatment for wood



Patented Apr. 21, 1942 v UNITED STATE Henri Marie Andi- Vautherin, Nancy, France, assignor of one-half to Pierre Schelameur and one-half to Yves Elie Marie Jacques de Llnlers, both of Saint Vit, France No Drawing. Application February 27, 1939,

Serial No. 258,857. In France MaI'ch 28, 1936 3 Claims.

My invention. is a continuation in part of my prior specificationSer'. No. 126,479.

My invention has for its object an improved protective treatment for wood which is more rapid than the treatments used hertoiore' which provide a progressive initial heating.

My invention has also for its object the retention inside'the wood'of all valuable distillation products with the omission of all preliminary kiln drying:

' It has further for its object the obtention of wood having an increased flexibility without any reduction of its mechanical properties and which shows even when impregnated with creosote and the like an unsoiled non-oily surface without any undue loading with water of the wood when treated in a dry condition.

Finally my invention proved commercial conditions in heating allowing .reduced size of boiler and weight of the autoclave chamber, together with a minimum time of storage for the cut-down wood.

The usual methods used for preserving wood consist in incorporating in the ligneous tissues a certain amount of foreign antiseptic or pro.-

tective substances.

Such methods also include application of heat has for its'object etof the wood which provide the destructive livin beings with the food required for their d'evelopment. There is formedby my novel. treatment inside the mass of the wood, at the expense oi these components, substances which are nonassimilable or poisonous for these destructive living beings. Moreover with a sufficiently long application of-a sufiiciently high temperature, the

wood is rendered entirely aseptic as no life can continue inside it. 1

For executing my invention, I introduce wood, preferably without its bark and in a state of mean dryness, although this is not necessary, inside a heat-insulated closed space, for instance inside an autoclave. This space is to be capable of resisting the internal pressure produced by reason of the evolution of the steam contained in the wood during the treatment.

I raise the tempera 'ure to a degree which de-.

pends on the nature 0 the wood treated and on the intensity of transformation which it is desired to obtain and this temperature is maineither to the wood itself or to the protective substance or to both.

But, chiefly in the case where heat is applied to the wood itself before impregnation, this action of heat is always limited to comparatively low temperatures and at any rate to temperatures under 120 C. It has generally for its object to produce a certain dryingv of the tissues, 1

which accounts for its being effected in kilns the atmosphere of which is more or less renewed so as to remove the moistness. A known method also consists-in drying the wood by immersing it in a fluid at a temperature suitable for exhausting or allowing the free boiling of the water contained in the wood considered.

My improved method for the preservation of wood consists in submitting it inside a closed heat-insulated steam chamber to temperatures comprised between 115 or 120 and 160 or even 170 C. during a time sufficient for obtaining a transformation of the tissues which renders them non-alterable and non-attachable.

I have found in fact thatthe chemical constitution of wood brought during suflicie'nt'time and inside a closed space limiting the carrying ofi of the moistness of the tissues, to sufficiently high'temperatures is submitted toa modification.

This modification chiefly affects the components tained during the time required for the transformation to reach the centre of the wood piece considered.

By way of example this result is achieved with moderately dry wood in pieces of about 20 cm.

thickness or diameter by maintaining the high I temperature during three to four hours. The cross-section of the wood effects a well-defined colour, which corresponds to-a well defined stage of transformation of the tissues for the nature of wood considered. For instance for resinous wood, this colour is pale yellow for treating temperatures between and and chocolatebrown for temperatures between and For the operation to be performed correctly it is necessary for the colour of the cross-section of the wood treated to become substantially uniform, which shows that the whole mass has really been submitted to the temperature of equilibrium during sufficient time.

As' far as aseptic conditions are concerned as well as specific gravity of the transformed ma terial, it is ofinterest' to adopt a temperature of operation as high as possible which does not affect the proper mechanical resistance of the material after treatment. This optimum temperature is about'150? C. for fir and spruce wood.

The treated wood acquires a greater flexibility than untreated wood. whichis frequently of advantage, for instancelin the case of poles used for electric and telephone wires.

The heating of the treating space is such as will providea very rapid rise in temperature at the beginning of operation, until the desired optimum temperature of treatment is reached. This optimum temperature is then maintained T until the wood is transformed as described. I

may us for the heating for instance steam radiators or the like. For increasing the speed of treatment it is preferable to introduce into the space at the beginning oi the operation, live steam at a pressure of 3 to '1 lags/cm. The radiator heating may begin at the end of the steam heating, i. e., when the optimum temperature is reached, say aiter 1 hour. But in practice I prefer associating first for a rapid rise in temperature steam and radiator heating and maintain-' ing the optimum temperature obtained by sole radiator heating. This limited introduction of steam allows thus a permanent atmosphere of steam to be produced without any condensation,

along the heat insulated walls in contradistinction with the prior stagnant bath of steam in which steam is continuously ted to make up for the steam continuously condensing againstthe unprotected-walls and washing out the wood which loses thus its valuable tarry constituents. It may be added that the body of steam furthers the transmission of the radiated heat during the .time required therefor, say 2% to 4 hours after optimum temperature is reached.

The introduction of live steamalso allows the application of antiseptic or insecticide vapours or mists. To this .end there is inserted in the steam admission circuit a heated container provided with a levelindicator and filled with an antiseptic or insecticide liquid. As it passes through this liquid, the steam carries it oii into the treatment space under the shape of a vapour or of a mist. The level indicator provides means for controlling the amounts of liquid carried "on by the live steam. This arrangement is applicable inter alia to the use of oily products such as cresote. The hot wood sucks the creosote mist in and shows a per ectly clean unsoiled surface after treatment, the antiseptic-mist providing protective iillingup material wood.

The temperature of the live steam should be raised to a suitable value, say 180 C. so as to produce a thorough movement of the product.

Care should be taken however to adjust the vention. Preferably this impregnation with creosote is performed before the rise in temperature provided by the steam bath containing or not a mist of an antiseptic orthe like products.

The penetration and the diffusion oi the antiseptic are considerably improved by the method according to'm'y invention and the suriace of the wood is much cleaner than with'the methodsused heretofore.

inside the according to the wood. It is about 130 to 135 C. for poplar, 188 to 145 for pine and beech, 142 to 148' for fir, spruce and larch, 145 to 150 for oak and ash. This temperature is reached as stated as rapidly' as possible so as to form almost immediately anv inner protection constituted by tarry components at the periphery, which pre-. vent any distilling off oi the inner valuable components oi the wood. The optimum temperature is easily ascertained by tests made successively say at 160 (2., 158, 156 and so on untilthe stresses required for breaking the test pieces remain substantially constant. This gives the maximum permissible temperature which is about 5 to 7 above the average optimum temperature.

It should be noted that the plant required for executing the process is very economical as the boiler has to produce only a small amount oi steam during a short time.

What I claim is:

1. In the preservation oi wood, the

160 0., the steam in contact withv the wood containing a mist oi an oily antiseptic substance, then shutting oii the direct steam heat and continuing the radiated heat until the transformed I color oi the wood becomes substantially uniform throughout, whereby the elasticity of the wood is increased and a dry non-oily surface is produced.

2.- In the preservation oi wood. the process which comprises placing wood to be preserved in a closed, heat-insulated, non-aerated space,

simultaneously heating said wood both with radiated heat and by direct contact with steam under pressures ranging from about 3 to '7 kilograms per square centimeter until the temperature 01' the wood is within the range of about 115 to 160 C., the steam in contact with the wood containing a mist of an oily antiseptic substance, then shutting oi! the direct steam heat and continuing the radiated heat until the transformed color oi ,the wood becomes substantially uniform throughout, the wood being impregnated with creosote before the completion of the process, whereby a highly elastic creosoted wood is produced having a dry non-oily surface.

3. In the preservation of wood, the process which comprises placing wood to be preserved in a closed, heat-insulated, non-aerated space, simultaneously heating said wood with radiated heat and by direct contact with steam under pressures ranging from about'3 to 7 kilograms per square centimeter until the wood reaches a temperature within the range of about to 0., thesteam in contact with the wood containing a mist of an oily antiseptic substance, then shutting oil? the direct steam heat and continuing the radiated heat until the transformed color of the wood becomes substantially uniform throughout, whereby the elasticity of the'wood is increased and a dry non-oily surface is produced.

.HENRI MARIE ANDRE VAUTHERIN.

' The optimum temperature of treatment varies 7 process" which comprises placing wood to be preserved in a' closed, heat-insulated, non-aerated space, simultaneously heating said wood both with radiated heat and by direct contact with steam under pressures ranging from about '3 to 7 kilograms per square centimeter until the temperature of 'the wood is within the range of about 115 to 

